mpc5200 slice timer problem

hi, I have just finished a driver of mpc5200 slice timer.I want to test it's PRECISION. I use DEC to help my work. here is the code:

unsigned int BUS_MHZ = 66;

void dec_init( unsigned int mhz ) { BUS_MHZ = mhz; }

void dec_sett(); asm(".text"); asm(".global dec_sett"); asm("dec_sett:"); asm("li 3,0xffffffff"); asm("mtdec 3"); asm("sync"); asm("isync"); asm("blr");

unsigned int dec_gett(); asm(".text"); asm(".global dec_gett"); asm("dec_gett:"); asm("mfdec 3"); asm("sync"); asm("isync"); asm("blr");

float dec_unit() { float f1; f1 = 4.0/BUS_MHZ;

return f1; }

void PPCTimeGet(float * sys_time) { *sys_time =(float )(0xffffffff - dec_gett())/((float )BUS_MHZ/4.0); }

I use these function like this:

#define WAIT_TICK 1 #define TICKPERUS 1000 //microsecond per ticks #define MAXRUNTIME 10

void Init(void ) { float curtime; unsigned i;

//enable Arbiter Configuration Register's TBEN bit MBAR_ACR_CFG |= 0x00002000;

//init the frequency of bus dec_init(66); dec_sett();

for (i = 0; i < MAXRUNTIME; i++) {

dec_sett();

sleep(WAIT_TICK )

PPCTimeGet(&curtime);

printf("%f\n",curtime - WAIT_TICK * TICKPERUS); } }

can any one give some advices about my code? I am not sure whether my code is correct or not. Or , if you have better idea, please tell me. thanks.